Daily Coding Challenges & Projects

Frontend Mini Project Challenge

Focus : HTML, CSS, and JavaScript

Build a "Dark Mode + Light Mode Toggle" using HTML, CSS, and JavaScript

Requirements :

• Add a toggle button (switch or icon).
• Store the user’s theme preference using localStorage.
• Smooth transition (CSS) between themes.
• Bonus : Animate the toggle using CSS transforms.

Hints :

• Add .dark-mode to and update styles.
• CSS transition: transition: background-color 0.3s, color 0.3s;
• JS : localStorage.setItem("theme", "dark")

Backend Challenge

Language Focus : Scala, R, Swift, TypeScript (Node.js + TS)

Scala Backend Challenge ( Akka HTTP ) :

Problem : Create an API endpoint:

GET /fibonacci/{n} → Return the n-th Fibonacci number.

• Use Akka HTTP routing.
• Handle invalid inputs with proper error messages.

R Backend Challenge (Data API) :

Problem : Build an R API endpoint using plumber :

• Route : /summary
• Accept CSV upload.
• Return mean, median, max, min of numeric columns.

Swift Backend Challenge ( Vapor ) :

Problem : Create a Vapor route :

POST /reverse

• Accepts JSON { "text": "Hello" }
• Returns { "result": "olleH" }

TypeScript Backend Challenge (Node.js + TS)

Problem : Create an API endpoint using Express + TypeScript :

GET /users/active

• Returns users active in the last 30 days.
• Validate using zod.

Database Query Challenge

Problems on SQL - HR Database :

1. Find all employees who have never received a salary increment.
2. Find the top 3 highest-paid employees in each department.

Data Structures & Algorithms Challenge

• Easy :
• Problem : Check if an array is a palindrome (same forward & backward).
• Hint : Compare arr[i] with arr[n-1-i].
• Medium :
• Problem : Given an array, return the length of the longest increasing subsequence (LIS).
• Hint :
• Use DP: dp[i] = LIS ending at i.
• Or binary search optimization.
• Hard :
• Problem : Design a data structure that supports:
• insert(x)
• delete(x)
• getRandom() — returns a random element in O(1).
• Hint :
• Use hash map + dynamic array.

Bug of the Day

Language Focus : Scala, R, Swift, TypeScript

Buggy Code ( Scala ) :

val numbers = List(1, 2, 3)
println(numbers.map(x => x * 2))
println(numbers(5)) // Bug

Task : Identify and fix.

Buggy Code ( R ) :

data <- data.frame(a=c(1,2,3))
print(mean(data))

Task :Why error? Fix using correct column selection

Buggy Code ( Swift ) :

let name: String? = nil
print(name.count)

Task : Fix nil handling.

Buggy Code ( TypeScript ) :

let val: number | string = 10;
console.log(val.toFixed(2)) // Bug?

📋 Daily Micro-Project

Focus : Backend

Task :

Create a small JWT Authentication Service

• /login → returns JWT
• /profile → verify JWT
• /logout → blacklist token
• Use any backend language (Scala/R/Swift/TS)

Bonus : Token expiry checker.

Trivia: 5 Fun Facts

• Set 1 :
• Python was named after "Monty Python."
• Java was originally called Oak.
• Linux was written by Linus Torvalds at age 21.
• WWW was invented by Tim Berners-Lee in 1989.
• Git was created by Linus Torvalds.
• Set 2 :
• The first computer bug was a real moth.
• JSON was created by Douglas Crockford.
• PHP originally stood for "Personal Home Page."
• Go was created at Google in 2007.
• React was open-sourced in 2013 by Facebook.
• Set 3 :
• SQL was developed at IBM in 1970s.
• The first website is still online.
• Linux mascot "Tux" was designed in 1996.
• C language was created at Bell Labs.
• The original name of JavaScript was Mocha.
• Set 4 :
• The first website is offline now.
• Gmail started as a 20% Google side project.
• Apple’s first logo showed Isaac Newton.
• Unicode has 150,000+ characters.
• The term “bug” dates back to 1878 (Edison).
• Set 5 :
• IBM’s ENIAC weighed 27 tons.
• Apple used to sell clothing in 1980s.
• MySQL is named after co-founder’s daughter (“My”).
• Python’s package installer is younger than the language.
• Rust won “most loved language” many years.

Tool & Resource of the Day

Tool : Postman

Best API testing & automation tool.

Resource Roundup :

• TypeScript Handbook (free)
• MDN Web Docs
• PostgreSQL Query Optimization Guide
• React Beta Docs
• "Scala at Light Speed" free PDF

Interview Question of the Day

Daily Interview Questions

Frontend :
1. What is the difference between v-if and v-show in Vue?
2. Explain event bubbling in JavaScript.
3. What causes React re-renders?
4. What is CSS specificity? How is it calculated?

Backend :
1. Explain immutability in Scala.
2. How does R handle vectorized operations?
3. What are optionals in Swift?
4. Explain TypeScript type narrowing.

Database :
1. What is a CTE?
2. Why use indexes?
3. Difference between GROUP BY and window functions?

Others :
1. What is CI/CD?
2. What does a load balancer do?

Daily Quiz Challenge

Frontend :

1. What does computed do in Vue?
2. CSS : What does transform: scale(1.2) do?
3. What is a React Hook?

Backend :

1. Scala : What is pattern matching?
2. R : What is a dataframe?
3. TypeScript : What is a union type?

Database :

1. What does the SQL HAVING clause do?

Other Tech :

1. What is a container image?

Mixed Quiz :

1. JS : Output of typeof null?
2. SQL : Purpose of ORDER BY?
3. Backend : What is an API?

Weekly Cross-Domain Activities ( December 05 to December 11, 2025 )

API of the Day:

Integrate OpenWeatherMap API

• Build /weather?city=
• Show temperature, humidity, conditions.

Linux / DevOps Tip :

10 commands to monitor server health :

top, htop, df -h, du -sh, ps aux, systemctl status, journalctl, iostat, free -m, uptime. 

Real-World Project of the Week ( December 05 to December 11, 2025 )

Project of the Week:

Build a Full Authentication System (frontend + backend + JWT).

Collaborative Project :

Contribute to an open-source:

Awesome-Dev-Templates GitHub repo.

Case Study :

Study how Twitter handles real-time updates (WebSockets, queues, caching).